The field of the disclosure relates generally to gas turbine engines and, more particularly, to a system and method of operating a gas turbine engine system during aircraft flight.
Aircraft powered by ducted fan propulsion systems use the ducted fan propulsion systems for all phases of flight. The engines are designed to provide sufficient power for take-offs, climbs, and cruise at different altitudes and different flight speeds. Given the many flight phases that must be accommodated by one engine model, there are likely some phases in which the engines perform less optimally than in other phases. For example, most of the aircraft's time is spent at altitude at a cruising speed. Consequently, the engines are designed to be most fuel efficient during cruise conditions. The engines also have to be sized sufficiently to safely propel the aircraft into the air at take-off. Take-off requires the engines to be sized larger than needed for cruise conditions, which introduces inefficiencies in the operation of the engines. The larger size engines also generate more thrust at idle speed than is needed for operation during certain flight conditions. For example, on approach to a runway, an aircraft may be instructed to maintain certain waypoints. If the distance between waypoints and the times when the aircraft is scheduled to arrive at those waypoints necessitates an aircraft speed less than the idle speed of the aircraft, measures to slow the aircraft are necessary or the aircraft may be rerouted to make another approach.